solution: day 19

data/examples/19.txt

@@ -0,0 +1,17 @@
+px{a<2006:qkq,m>2090:A,rfg}
+pv{a>1716:R,A}
+lnx{m>1548:A,A}
+rfg{s<537:gd,x>2440:R,A}
+qs{s>3448:A,lnx}
+qkq{x<1416:A,crn}
+crn{x>2662:A,R}
+in{s<1351:px,qqz}
+qqz{s>2770:qs,m<1801:hdj,R}
+gd{a>3333:R,R}
+hdj{m>838:A,pv}
+
+{x=787,m=2655,a=1222,s=2876}
+{x=1679,m=44,a=2067,s=496}
+{x=2036,m=264,a=79,s=2244}
+{x=2461,m=1339,a=466,s=291}
+{x=2127,m=1623,a=2188,s=1013}

src/bin/19.rs

@@ -0,0 +1,387 @@
+use std::{
+    collections::HashMap,
+    ops::{Index, IndexMut},
+    str::FromStr,
+};
+
+#[derive(Debug, Hash, PartialEq, Eq, Clone, Copy)]
+enum Gear {
+    X,
+    M,
+    A,
+    S,
+}
+
+#[derive(Debug)]
+struct GearParseError;
+
+impl TryFrom<&str> for Gear {
+    type Error = GearParseError;
+    fn try_from(value: &str) -> Result<Self, Self::Error> {
+        use Gear::*;
+        Ok(match value {
+            "x" => X,
+            "m" => M,
+            "a" => A,
+            "s" => S,
+            _ => return Err(GearParseError),
+        })
+    }
+}
+
+#[derive(Debug, Hash, PartialEq, Eq)]
+enum Comparator {
+    Lt,
+    Gt,
+}
+
+#[derive(Debug)]
+struct ComparatorParseError;
+
+impl TryFrom<char> for Comparator {
+    type Error = ComparatorParseError;
+    fn try_from(value: char) -> Result<Self, Self::Error> {
+        use Comparator::*;
+        Ok(match value {
+            '<' => Lt,
+            '>' => Gt,
+            _ => return Err(ComparatorParseError),
+        })
+    }
+}
+
+#[derive(Debug, Hash, PartialEq, Eq, Clone)]
+enum Resolver {
+    Accepted,
+    Rejected,
+    Delegated(String),
+}
+
+impl From<&str> for Resolver {
+    fn from(value: &str) -> Self {
+        use Resolver::*;
+        match value {
+            "A" => Accepted,
+            "R" => Rejected,
+            x => Delegated(x.to_string()),
+        }
+    }
+}
+
+#[derive(Debug, Hash, PartialEq, Eq)]
+struct Workflow {
+    workflows: Vec<WorkflowInner>,
+}
+
+#[derive(Debug)]
+struct ParseWorkflowError;
+
+impl TryFrom<&str> for Workflow {
+    type Error = ParseWorkflowError;
+    fn try_from(value: &str) -> Result<Self, Self::Error> {
+        Ok(Self {
+            workflows: value.split(',').filter_map(|x| x.try_into().ok()).collect(),
+        })
+    }
+}
+
+#[derive(Debug, Hash, PartialEq, Eq)]
+enum WorkflowInner {
+    Resolver(Resolver),
+    Rule((Gear, Comparator, usize, Resolver)),
+}
+
+#[derive(Debug)]
+struct ParseWorkflowInnerError;
+
+impl TryFrom<&str> for WorkflowInner {
+    type Error = ParseWorkflowInnerError;
+    fn try_from(value: &str) -> Result<Self, Self::Error> {
+        if !value.contains(':') {
+            return Ok(WorkflowInner::Resolver(Resolver::from(value)));
+        }
+
+        let (rest, resolver) = value.split_once(':').unwrap();
+        let resolver = Resolver::from(resolver);
+
+        let (gear, number) = rest.split_once(|x| x == '<' || x == '>').unwrap();
+        let gear = Gear::try_from(gear).map_err(|_| ParseWorkflowInnerError)?;
+        let number = number.parse().map_err(|_| ParseWorkflowInnerError)?;
+
+        let comparator = if value.contains('<') { '<' } else { '>' };
+        let comparator = Comparator::try_from(comparator).map_err(|_| ParseWorkflowInnerError)?;
+
+        Ok(WorkflowInner::Rule((gear, comparator, number, resolver)))
+    }
+}
+
+#[derive(Debug)]
+struct Xmas {
+    x: usize,
+    m: usize,
+    a: usize,
+    s: usize,
+}
+
+#[derive(Debug)]
+struct ParseXmasError;
+
+impl FromStr for Xmas {
+    type Err = ParseXmasError;
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let s = s.strip_prefix('{').ok_or(ParseXmasError)?;
+        let s = s.strip_suffix('}').ok_or(ParseXmasError)?;
+        let xmas: Vec<_> = s
+            .split(',')
+            .filter_map(|x| x.split_once('='))
+            .map(|x| x.1)
+            .filter_map(|x| x.parse().ok())
+            .collect();
+
+        Ok(Self {
+            x: xmas[0],
+            m: xmas[1],
+            a: xmas[2],
+            s: xmas[3],
+        })
+    }
+}
+
+impl Index<Gear> for Xmas {
+    type Output = usize;
+    fn index(&self, index: Gear) -> &Self::Output {
+        use Gear::*;
+        match index {
+            X => &self.x,
+            M => &self.m,
+            A => &self.a,
+            S => &self.s,
+        }
+    }
+}
+
+impl IndexMut<Gear> for Xmas {
+    fn index_mut(&mut self, index: Gear) -> &mut Self::Output {
+        use Gear::*;
+        match index {
+            X => &mut self.x,
+            M => &mut self.m,
+            A => &mut self.a,
+            S => &mut self.s,
+        }
+    }
+}
+
+impl Xmas {
+    fn sum(&self) -> usize {
+        self.x + self.m + self.a + self.s
+    }
+
+    fn apply(&self, workflow: &Workflow) -> Resolver {
+        for w in workflow.workflows.iter() {
+            match w {
+                WorkflowInner::Resolver(x) => {
+                    return x.clone();
+                }
+                WorkflowInner::Rule((g, c, n, r)) => {
+                    let is_match = match c {
+                        Comparator::Gt => self[*g] > *n,
+                        Comparator::Lt => self[*g] < *n,
+                    };
+                    if is_match {
+                        return r.clone();
+                    }
+                }
+            }
+        }
+
+        unreachable!()
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+struct XmasRange {
+    x: (usize, usize),
+    m: (usize, usize),
+    a: (usize, usize),
+    s: (usize, usize),
+}
+
+impl Index<Gear> for XmasRange {
+    type Output = (usize, usize);
+    fn index(&self, index: Gear) -> &Self::Output {
+        use Gear::*;
+        match index {
+            X => &self.x,
+            M => &self.m,
+            A => &self.a,
+            S => &self.s,
+        }
+    }
+}
+
+impl IndexMut<Gear> for XmasRange {
+    fn index_mut(&mut self, index: Gear) -> &mut Self::Output {
+        use Gear::*;
+        match index {
+            X => &mut self.x,
+            M => &mut self.m,
+            A => &mut self.a,
+            S => &mut self.s,
+        }
+    }
+}
+
+impl XmasRange {
+    fn size(&self) -> usize {
+        (self.x.1 - self.x.0 + 1)
+            * (self.m.1 - self.m.0 + 1)
+            * (self.a.1 - self.a.0 + 1)
+            * (self.s.1 - self.s.0 + 1)
+    }
+
+    fn divide(self, workflow: &Workflow) -> Vec<(Self, Resolver)> {
+        let mut processed = Vec::new();
+        let mut rest = vec![self];
+
+        for w in workflow.workflows.iter() {
+            let mut new_rest = Vec::new();
+
+            while let Some(xmas_range) = rest.pop() {
+                match w {
+                    WorkflowInner::Resolver(r) => processed.push((xmas_range, r.clone())),
+                    WorkflowInner::Rule((g, c, n, r)) => {
+                        let compare = |x: usize, y: usize| match c {
+                            Comparator::Gt => x > y,
+                            Comparator::Lt => x < y,
+                        };
+
+                        let mut min_ok = usize::MAX;
+                        let mut max_ok = usize::MIN;
+                        let mut min_e = usize::MAX;
+                        let mut max_e = usize::MIN;
+
+                        for i in xmas_range[*g].0..=xmas_range[*g].1 {
+                            if compare(i, *n) {
+                                max_ok = if max_ok < i { i } else { max_ok };
+                                min_ok = if min_ok > i { i } else { min_ok };
+                            } else {
+                                max_e = if max_e < i { i } else { max_e };
+                                min_e = if min_e > i { i } else { min_e };
+                            }
+                        }
+
+                        if min_e <= max_e {
+                            let mut r = xmas_range;
+                            r[*g] = (min_e, max_e);
+                            new_rest.push(r);
+                        }
+                        if min_ok <= max_ok {
+                            let mut p = xmas_range;
+                            p[*g] = (min_ok, max_ok);
+                            processed.push((p, r.clone()));
+                        }
+                    }
+                }
+            }
+
+            rest = new_rest;
+        }
+
+        processed
+    }
+}
+
+fn build_map(input: &str) -> HashMap<&str, Workflow> {
+    let mut map = HashMap::new();
+    for (s, w) in input
+        .split("\n\n")
+        .next()
+        .unwrap()
+        .lines()
+        .filter_map(|x| x.strip_suffix('}'))
+        .filter_map(|x| x.split_once('{'))
+        .filter_map(|(s, w)| Workflow::try_from(w).ok().map(|x| (s, x)))
+    {
+        map.insert(s, w);
+    }
+
+    map
+}
+
+pub fn part_one(input: &str) -> Option<usize> {
+    let map = build_map(input);
+    let xmas_vec: Vec<Xmas> = input
+        .split("\n\n")
+        .nth(1)?
+        .lines()
+        .filter_map(|x| x.parse().ok())
+        .collect();
+
+    let mut total = 0;
+
+    'outer: for xmas in xmas_vec.into_iter() {
+        let mut workflow = &map["in"];
+        'apply: loop {
+            match xmas.apply(workflow) {
+                Resolver::Accepted => break 'apply,
+                Resolver::Rejected => continue 'outer,
+                Resolver::Delegated(x) => workflow = &map[x.as_str()],
+            }
+        }
+
+        total += xmas.sum();
+    }
+
+    Some(total)
+}
+
+pub fn part_two(input: &str) -> Option<usize> {
+    let map = build_map(input);
+
+    let mut finished = Vec::new();
+    let mut stack = vec![(
+        XmasRange {
+            x: (1, 4000),
+            m: (1, 4000),
+            a: (1, 4000),
+            s: (1, 4000),
+        },
+        Resolver::Delegated("in".to_string()),
+    )];
+
+    while let Some((xmas_range, resolver)) = stack.pop() {
+        match resolver {
+            Resolver::Accepted => finished.push(xmas_range),
+            Resolver::Rejected => {
+                continue;
+            }
+            Resolver::Delegated(x) => {
+                let workflow = &map[x.as_str()];
+                stack.append(&mut xmas_range.divide(workflow))
+            }
+        }
+    }
+
+    Some(finished.iter().map(XmasRange::size).sum())
+}
+aoc::solution!(19);
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_part_one() {
+        assert_eq!(
+            part_one(&aoc::template::read_file("examples", 19)),
+            Some(19114)
+        );
+    }
+    #[test]
+    fn test_part_two() {
+        assert_eq!(
+            part_two(&aoc::template::read_file("examples", 19)),
+            Some(167409079868000)
+        );
+    }
+}